What is a map? By this, I mean to ask what is a formal map, of the kind that historians are most likely to study (your kitchen-table imaginary tracing is an informal, ephemeral map). It is almost impossible to arrive at a single authoritative definition of what constitutes a map. There are too many varieties of map-like sketches, too many pictures that look like maps and maps that look like pictures, too many ephemeral representations of spatial relations for us to say simply and finally what a map is and isnt. Geographers and cartographers are continuously embroiled in ongoing debate about this very question. But without doing disservice to this rich discussion, we might distill the conventional wisdom about maps to a few key elements:

A map is a representation of space or place, or of phenomena as they exist in space. A map portrays geographical features, spatial features, or a geography. A map can be of micro-space (the layout of your bedroom), or of the biggest expanse we know, perhaps a schematic of the cosmos.

A map represents three-dimensional reality, but usually it is drawn on a flat two-dimensional plane (often a piece of paper). To translate effectively between these dimensions, the mapmaker employs various cartographic devices, especially scale and projection. Most maps have formal elements printed right on the map that give you guidance about how the mapmaker has represented the scene: directional information, keys, and scales are part of most maps. In the next section youll learn how to use these devices.

A map is much smaller than its subject, sometimes by astonishing degrees of magnitudefor example, a map of the largest country in the world (Russia) might be rendered on a piece of paper as small as an index card. Because of this size differential between real geography and mapped geography, mapmakers must be selectivea map cant represent all of reality in absolute terms, but only some parts of reality. Which parts of reality get included on a map varies: first of all, selectivity is determined by the mechanics of drafting and the limitations inherent in drawing big objects on small pieces of paper; but selectivity is also subjective and which parts of reality get put on a map depends on the purpose of the map, the mapmakers intentions, and the mapmakers biases and preferences.